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A Level Chemistry 1 > Kinetics > Flashcards

Kinetics Flashcards

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1
Q

define rate of reaction

A
  • how quickly a reaction happens
  • the rate of change in concentration
  • depends on how quickly the concentration of reactant or product changes with time
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2
Q

Rate of reaction equation

A

increase in product conc/ time taken
OR
decrease in reactant con/time taken

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3
Q

What unit is rate expressed in?

A

moldm-3s-1

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4
Q

What does a curved graph instead of a straight line tell us?

A

the gradient is not constant

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5
Q

How can you measure the rate of reaction on a graph?

A

draw a tangent to the curve at the time asked for

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6
Q

Why is the rate of reaction greater at the start of the reaction?

A

There is a greater reactant concentration

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7
Q

How would you measure rate of reaction if:

a. reaction produces colored precipitate
b. reaction produces gas

A

a. measure change in color

b. measure change in volume or mass of gas

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8
Q

Explain how to set up 2 experiments to measure the volume of gas produced.

A
  • gas syringe moves outwards as gas collects

- gas collected by displacement of water from inverted burette. Gas has to have low solubility in water

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9
Q

Explain how to set up experiment measuring the change in mass.

A
  • on digital balance, set beaker with cotton wool to prevent escape of liquid and solid
  • but some gases are too light to show changes in mass
  • needs continuous readings
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10
Q

kinetic molecular theory

A

particles in a substance move randomly because of the kinetic energy they possess

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11
Q

Do all particles in a substance have the same energy?

A

No. The random nature of movement and collisions means particles will have a range of energy values

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12
Q

What is the best way to measure the kinetic energy of a substance?

A

Take the average of the energy values of each molecule, and relate it to absolute temperature (temp measured in kelvin)

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13
Q

What does the Maxwell- Boltzmann distribution curve show?

A

Particles in a gas at a particular temperature show a range in their kinetic energy values

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14
Q

What is plotted on x and y axis in Maxwell-Boltzmann distribution curve?

A

x- kinetic energy

y- number of particles with kinetic energy

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15
Q

How do reactions occur?

A
  • reactants placed together
  • kinetic energy that particles possess cause them to collide with each other
  • result: bonds between reactants broken, bonds form. Thus, products form
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16
Q

What is the collision theory?

A
  • particles must collide
  • particles must have sufficient energy
  • particles must collide with correct orientation
17
Q

What do many collisions lack?

A

Sufficient energy and correct orientation to break bonds of reactant

18
Q

Activation Energy

A

energy required for reaction to take place

19
Q

What are the factors affecting the rate of reaction?

A
  • temperature
  • concentration
  • particle size
  • pressure
  • catalyst
20
Q

Why is activation energy necessary?

A
  • to overcome repulsion between molecules

- to break some bonds in reactants before they can react

21
Q

Draw and label an endothermic graph

A

(look in book)

22
Q

Draw and label an exothermic graph

A

(look in book)

23
Q

Which particles can have successful collisions?

A

Particles that have a kinetic energy value greater than the activation energy will have successful collisions.

24
Q

Do reactions with high or low activation energy proceed faster?

A
  • high Ea reactions are slow

- low Ea reactions are faster

25
Q

Explain the affect of temperature on the rate of reaction

A

increase in temp

  • increase in average kinetic energy
  • increase in collisions, moving faster
  • higher proportion of molecules have activation energy, more successful collisions

+affects sufficient energy and collision frequency

26
Q

Explain the affect of particle size on the rate of reaction

A
  • decreasing particle size (increasing surface area) increases rate of reaction, i.e. powder

+affects collision frequency

27
Q

Explain the affect of pressure on the rate of reaction

A
  • increases number of collisions

+affects frequency of collisions

28
Q

Explain the affect of a catalyst on the rate of reaction

A
  • increase rate of reaction by lowering Ea, by providing an alternate pathway
  • lower reaction energy by providing surface for reaction and weakening bonds

+affects collisions

29
Q

Explain the affect of concentration on the rate of reaction

A

-increase concentration: increases rate of reaction

+affects collision frequency and successful collisions

30
Q

How do catalysts lower reactivation energy?

A
  • Providing surface for reaction

- Weakening bonds of reactants

31
Q

What is the effect of temperature on a Maxwell- Boltzman distribution graph?

A
  • at higher temperature- more particles have kinetic energy value greater than Ea
  • at low temperature- less particles have kinetic energy value greater than Ea
32
Q

Define and state the advantage and disadvantage to heterogenous catalysts.

A
  • catalysts in different state than reactant
  • easy to remove
  • doesn’t spread easily
33
Q

Define and state the advantage and disadvantage to homogenous catalysts.

A
  • same state as reactant
  • mixes easily
  • difficult to remove`
34
Q

State the techniques for measuring the rates of reaction. (6 ways)

A

Measuring

  • change in volume of gas
  • change in mass
  • change in transmission of light: colorimetry/ spectrophometry
  • change in concentration measured by titration
  • change in concentration measured using conductivity
  • non-continuous methods of detecting change during a reaction - clock reactions
35
Q

Describe how to measure the rates of reaction through the change in transmission of light.

A
  • indicator added sometimes to generate color
  • colorimeter or spectrometer passes light of specific wavelength through solution
  • measures intensity of light transmitted by reaction components
  • substances with higher concentration absorb more light, therefore transmitting less
  • photocell generates electric current according to light transmitted
  • continuous readings
  • determine rate of reaction by measuring decrease in absorbance
36
Q

Describe how to measure the rate of reaction through the change in concentration measured using titration.

A
  • measure concentration of one of reactants or products by titrating it against known standard
  • no continous readings
  • identify: reactant and product includes water
37
Q

Describe how to measure the rate of reaction through the change in concentration measured using electricity

A
  • electrical conductivity or a solution depends on total concentration of its ions and charges
  • measured using conductivity meter
  • measure difference in concentration of ions between reactants and products
  • decrease in concentration of ions- decrease in electrical conductivity
  • identify: metals, Br, Al
38
Q

Describe how to measure the rate of reaction through the non-continuous methods of detecting change during a reaction: clock reactions

A
  • measure time it takes for reaction to reach observable fixed point
  • enact same reaction under different conditions, find different timings, and judge different rates of reaction
39
Q

True or false: are rate and time indirectly proportional?

A

True- rate= 1/time

A Level Chemistry 1 (11 decks)

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